THE axiom is as old as human striving: The per fect is the enemy of the good. In politics, this means that insisting on perfection in a candidate interferes with selecting a satisfactory one.

Which is why the mood of many of the 6,300 people, lots of them college age, who registered at last week’s Conservative Political Action Conference in Washington, was unreasonably morose. Sponsored annually by the American Conservative Union, CPAC is the conservative movement’s moveable feast. Many at CPAC seemed depressed by the fact, as they see it, that the top three Republican candidates – John McCain, Mitt Romney and Rudy Giuliani – are flawed. Such conservatives should conduct a thought experiment.

Suppose someone seeking the presidential nomination had, as a governor, signed the largest tax increase in his state’s history and the nation’s most permissive abortion law. And by signing a law institutionalizing no-fault divorce, he had unwittingly but substantially advanced an idea central to the campaign for same-sex marriages – the minimalist understanding of marriage as merely a contract between consenting adults to be entered into or dissolved as it suits their happiness.

Question: Is it not likely that such a presidential aspirant would be derided by some of today’s fastidious conservatives? A sobering thought, that, because the attributes just described were those of Ronald Reagan.

Now, consider today’s three leading candidates, starting with McCain, the mere mention of whose name elicited disapproving noises at CPAC. This column holds the Olympic record for sustained dismay about McCain’s incorrigible itch to regulate political speech (“campaign-finance reform”). But it is not incongruous that he holds Barry Goldwater’s Senate seat.

McCain, whose career rating from ACU is 82 (100 being perfect), voted in 2003 against the prescription-drug entitlement because of its cost. He is a strong critic of corporate welfare. And since 2003 he has been insisting that the mission in Iraq requires more troops – even more than will be there during the current “surge.”

Conservatives’ anger about McCain coexists with others’ discordant criticism of him for “pandering” to conservatives. Astonishingly, a recent Vanity Fair profile accused McCain of “toeing the conservative line” on immigration, which shows that Vanity Fair does not know what that line is.

The journalistic rule is that conservatives pander, liberals “grow.” When Al Gore, Dick Gephardt, Jesse Jackson and Dennis Kucinich changed from being pro-life to pro-abortion, their conversions, which were a price of admission into Democratic presidential politics, were often described as conscientious “growth.” But when McCain, who opposed Bush’s tax cuts, concludes on the basis of the humming economy that they should be made permanent, this is called pandering.

At CPAC, Romney gave the most polished speech, touching all the conservative movement’s erogenous zones, pointedly denouncing the “McCain-Kennedy” immigration bill and promising to seek repeal of the McCain-Feingold law regulating campaign speech.

Many conservatives, however, criticize Romney for what they consider multiple conversions of convenience – on abortion, stem-cell research, gay rights, gun control. But if Romney is now locked into positions that these conservatives like, why do they care so much about whether political calculation or moral epiphany moved him there?

Giuliani is comprehensively out of step with social conservatives, and likely to remain so. He probably assumes two things.

First, that some of the social issues have gone off the boil because argument about them seems sterile: Democrats have scant interest in federal gun-control legislation; scientific advances may obviate the need for using stem cells; cultural changes will do more than any feasible legislation can do to reduce abortion numbers; the way to change abortion law is to change courts by means of judicial nominations of the sort Giuliani promises to make.

Second, that his deviations from the social conservatives’ agenda is more than balanced by his record as mayor of New York. That city was liberalism’s laboratory as it went from the glittering metropolis celebrated in the movie “Breakfast at Tiffany’s” (1961) to the dystopia of the novel “Bonfire of the Vanities” (1987). Giuliani successfully challenged the culture of complaint that produced the politics of victimhood that resulted in government by grievance groups.

He favors school choice, he opposes bilingual education that confines students to linguistic ghettos and he ended the “open admissions” policy that degraded City University, once an effective instrument of upward mobility. The suggestion that 9/11 required city tax increases triggered from Giuliani four adjectives: “dumb, stupid, idiotic and moronic.”

Conservatism comes in many flavors. None seems perfect for every conservative’s palate; most should be satisfactory to most conservatives.